After the disappointment of the barbecue summer it might not be too late for a barbecue autumn. There will be dry weather and some balmy conditions across much of Britain this week, with temperatures increasing towards 20C (68F). Some weather forecast models are even expecting close to record warmth for mid-October.

The calm conditions are because of a high-pressure system settling over Britain and blocking out the wet and windy weather from the Atlantic. Just like last month’s long dry spell, this weather pattern could hold for a week or more. Perhaps the decent weather goes some way to redeeming the summer washouts and it is good news for the fruit harvest, with a record-breaking crop of plums, an outstanding harvest of apples and pears and the promise of a vintage year for English vineyards.

The warm weather has also boosted butterflies, with clouded yellow, large white, painted lady and red admiral butterflies invading late from Europe.

There are, however, signs of a drought in Eastern England, where East Anglia had only 16.5mm (0.65in) rainfall last month, 30 per cent of its normal amount. The ground has turned so hard that it is difficult for farmers to harvest potatoes without bruising them, and councils in Norwich and Great Yarmouth have closed football and rugby pitches to prevent injuries because of the hard ground.

The dry, sunny days could also bring out some magnificent leaf colours, with the first tints beginning to show in most parts of the country.

“Sunny days, dry weather and cool nights are the perfect conditions for autumn tree colours,” said Kate Lewthwaite, project manager for Nature’s Calendar initiative at the Woodland Trust.

“The warm days concentrate the sugar in the leaf and bring out the coloured pigments, while the green chlorophyll breaks down in the cool nights.”

This is the classic Indian summer — a spell of calm, warm, sunny weather in October or November. “Sometimes the rain is followed by an interval of calm and warmth which is called the Indian summer; its characteristics are a tranquil atmosphere and general smokiness,” wrote North American farmer, John de Crèvecoeur, in 1778, in what is possibly the first record of an such an autumn.

The conditions he described are typical of an anticyclone, when the American Indians took advantage of the calm conditions to set fire to prairie grass, brush and woods and created smoky air to flush out prey and give the hunters cover to stalk the animals.